Hello everyone, A while back I asked about this on the LVM mailing list, but didn't receive a response. Am revisiting it now, so would like a broader audience. I've run into some substantial read slowness when using dump or tar to backup filesystems that are stored on LVM2 LVs. All of my tests are dumping ext3 filesystems to /dev/null. I'm seeing speeds in the range of 3-4MiB/s. If I increase dump's blocksize to 128KiB records, speed jumps up to about 20KiB/s, which is better but still frustratingly slow. Going to 1024KiB gets me about 28MiB/s. Today I loop mounted a file on my LVM, filled it up with some crap from urandom and dumped it out. I was able to get 50-60MiB/s. Is this amount of performance loss due to dm expected? My LV is just two SATA hard disks that I put into a VG. Stupid benchmarks with dd gives me a raw read speed from the LV of about 60MiB/sec. I'm using kernel 2.6.18-4-686 from debian. Any ideas on what's slowing down dump? -- Ross Vandegrift ross@xxxxxxxxxxx "The good Christian should beware of mathematicians, and all those who make empty prophecies. The danger already exists that the mathematicians have made a covenant with the devil to darken the spirit and to confine man in the bonds of Hell." --St. Augustine, De Genesi ad Litteram, Book II, xviii, 37 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
